Soap kills viruses by physically tearing apart their fatty outer layers.

Soap molecules are amphiphilic, meaning they contain both a hydrophilic (water-loving) head and a hydrophobic (water-fearing) tail. Viruses like SARS-CoV-2 and influenza are 'enveloped' viruses, protected by a lipid bilayer made of fatty molecules. When you wash your hands, the hydrophobic tails of the soap molecules are attracted to the virus's fatty membrane and wedge themselves into it like crowbars.This action disrupts the chemical bonds holding the virus together, causing the entire structure to fall apart. According to Palli Thordarson, a chemistry professor at the University of New South Wales, soap is more effective than most disinfectants because it mechanically destroys the virus's foundation. While hand sanitizers with at least 60% alcohol also disrupt this layer, they do not physically wash the viral fragments off the skin like soap and water do.The Centers for Disease Control and Prevention (CDC) recommends scrubbing for at least 20 seconds to ensure the soap molecules have enough time to interact with every fold of the skin. During this time, the soap also traps dirt and destroyed viral particles in tiny bubbles called micelles. These micelles are then easily rinsed away by running water. This combination of chemical destruction and physical removal makes handwashing one of the most powerful tools in public health.